Indirect Exam 1 Flashcards
Describe an optimal restoration
Combo of biologic, mechanical, and esthetic properties
Which property?
Retention form
Mechanical
Which property?
Resistance form
Mechanical
Which property?
Deformation
Mechanical
Which property?
Conservation of tooth structure
Biologic
Which property?
Avoidance of overcontouring
Biologic
Which property?
Supragingival margins
Biologic
Which property?
Harmonious occlusion
Biologic
Which property?
Protection against tooth fracture
Biologic
Which property?
Minimum display of metal
Esthetic
Which property?
Max thickness of porcelain
Esthetic
Which property?
Porcelain occlusal surfaces
Esthetic
Which property?
Subgingival margins
Esthetic
Name 3 biological considerations
Adjacent teeth
Soft tissue
Pulp
How can soft tissue damage be prevented?
Retraction with aspirator tip, mirror, or isolite
What are 4 biological considerations in regards to the pulp?
Pulp size
Temp
Chemical action
Bacterial action
Name the 6 ways we can conserve tooth structure
- Partial coverage rather than complete coverage
- Prep of teeth with minimum practical convergence angle (taper) btwn axial walls
- Prep occlusal surface so reduction follows anatomical planes (gives uniform thickness to restoration)
- Prep axial surfaces so tooth structure is removed evenly
- Select conservative margin compatible with other principles of tooth prep
- Avoid unnecessary apical extension
The more apical the margin (subgingival), the __________ (more/less) conservative
less
What are the 4 types of crown materials?
PFM
PFZ
Monolithic ceramic
Full metal
Margin = ?
Finish line
What are the types of margin designs?
Bevel
Chamfer
Shoulder
Feather-edge
Which type of margin?
Advantages:
Removes unsupported enamel
Allows finishing of metal
Bevel margin
Which type of margin?
Disadvantage:
Can extend prep into sulcus
Bevel margin
Which type of margin?
Indications:
Facial margin of maxillary partial-coverage restorations
Inlay/onlay margins
Bevel margin
Which type of margin?
Advantages:
Fewer complications
Adequate bulk
Chamfer margin
Which type of margin?
Disadvantage:
J-lip
Chamfer margin
Which type of margin?
Indications:
Full metal, PFM, and some ceramics
Chamfer margin
Which type of margin?
Advantage:
Bulk of restorative material
Shoulder margin
Which type of margin?
Disadvantage:
Less conservative
Shoulder margin
Which type of margin?
Indications:
Facial margin of PFM crowns
All ceramic crowns
Shoulder margin
Which type of margin?
Advantage:
Conservative prep
Feather-edge margin
Which type of margin?
Disadvantages:
Not sufficient bulk
Requires metal margin
Feather-edge margin
Which type of margin?
Indication:
Long preps
Feather-edge margin
What are the 3 possible margin placements?
Supragingival
Epigingival
Subgingival
Which margin placement?
Easily finished, easily kept clean
Supragingival
Which margin placement?
Impressions easier to get without damaging soft tissue
Supragingival
Which margin placement?
Restorations can be easily evaluated at recall appts
Supragingival
Which margin placement?
Not ideal, places interface tooth/restoration right on gingival crest
Epigingival
Which margin placement?
Can create inflammation and gingivitis
Epigingival
Which margin placement?
More esthetic
Subgingival
Which margin placement?
Provides additional crown retention
Subgingival
Which margin placement?
Root sensitivity
Subgingival
Which margin placement?
Not indicated in pts with caries, erosion, subgingival restorations, and crown lengthenings
Subgingival
What are the occlusal considerations mentioned in lecture?
Rollercoaster
Supraerupted
Occlusal trauma
Titlted teeth
Feature of a tooth prep that resists dislodgement of a crown in a vertical direction or along path of placement
Retention form
Features of a tooth prep that enhance stability of a restoration and resist dislodgement along an axis other than the path of placement
Resistance form
Why should you prep with a green or black label diamond with heavy grit?
The rougher the surface better
Which gold alloys are used for intracoronal cast restorations?
Type I and II
Which gold alloys are used for crowns and FDPs?
Type III and IV
The thicker the cement, the __________ (stronger/weaker) the strength
weaker
The higher the SA, the _____________ (better/worse) the retention
better
The higher the axial walls, the ___________ (higher/lower) the SA
higher
The wider the prepped tooth, the ___________ (higher/lower) the SA
higher
What can cause a crown to dislodge?
Sticky food like caramel
What should be the degree of convergence of your prep?
6-10 degrees
Reduces stress on remaining tooth structure
Rounded internal line angles (no sharp edges!)
What is the ideal vs acceptable taper?
Ideal = 6-10 degrees
Acceptable = 10-20 degrees
How can you improve the resistance and retention of a crown in the case of a virgin tooth?
6-10 degree convergence
Conservative prep
Lower margins to have longer axial walls
What material can you use to improve the resistance and retention of a crown?
Stronger cement (ex: Panavia, a resin cement)
How can you improve the resistance and retention of a crown in the case of replacing or prepping a tooth that already has lost significant structure?
Retentive grooves
Prepare wider margin to reduce convergence
Build-up with pins
Long narrow channel or depression, such as indentation btwn tooth cusps or retentive features placed on tooth surfaces to augment the retentive characteristics of crown preps
Groove
A mesial and distal groove helps protect from what type of dislodgement?
Bucco-lingual dislodgement
A buccal and lingual groove helps protect from what type of dislodgement?
Mesio-distal dislodgement
What are the 7 key principles of preps?
Conservation of tooth structure
Resistance form
Retention form
Structural durability
Marginal integrity
Preservation of the periodontium
Aesthetic considerations
Which key principle of preps?
To avoid weakening tooth unnecessarily
Conservation of tooth structure
Which key principle of preps?
To avoid compromising the pulp
Conservation of tooth structure
Which key principle of preps?
To prevent dislodgment of a cemented restoration by apical or obliquely-directed forces
Resistance form
Which key principle of preps?
To prevent displacement of a cemented restoration along any of its paths of insertion, including long axis of the prep
Retention form
Which key principle of preps?
To provide enough space for a crown that is sufficiently thick to prevent fracture, distortion, or perforation
Structural durability
Which key principle of preps?
To prepare a finish line to accommodate a robust margin with close adaptation to minimize microleakage
Marginal integrity
Which key principle of preps?
To shape the prep so the crown is not over-contoured and its margin is accessible for optimal oral hygiene
Preservation of periodontium
Which key principle of preps?
To create enough space for aesthetic veneers where indicated
Aesthetic considerations
Specific direction in which a prosthesis is placed on the abutment teeth or implant
Path of placement/insertion/withdrawal
When visualizing the path of placement, how should you look at the center of the occlusal surface of your prep?
With 1 eye closed
What should be seen from the ideal path of insertion?
Prepped tooth
The path of placement helps to ensure the prep is not ____________ or _______________
undercut; overtapered
When visualizing the path of placement, what should be able to be seen at 360 degrees?
Margin (finish line)
When using indirect vision to visualize the path of placement, when should you stop maneuvering the mirror?
When prep is centered
What is the path of placement for posterior teeth?
Perpendicular to occlusal plane
What is the path of placement for maxillary posterior teeth?
Slightly buccal
What is the path of placement for mandibular posterior teeth?
Slightly lingual
What is the path of placement for anterior teeth?
Flared to facial, finding a mid-point btwn the abutment’s tooth axis
What classification of dental alloy?
Type I
Inlays
What classification of dental alloy?
Type II
Onlays
What classification of dental alloy?
Type III
Crowns/FDPs
What classification of dental alloy?
Type IV
RPDs
Type I hardness
Soft
Type II hardness
Medium
Type III hardness
Hard
Type IV hardness
Extra hard
What type of dental alloy?
PFM and Full Metal crowns
Type III
7 requirements for PFM crowns
High fusion temp to withstand porcelain firing
Thermal coefficient of expansion > than porcelain
Promote durable metal/porcelain bond
High mechanical properties
Biocompatible
Tarnish resistance
Usually nickel free
What are the available alloy systems?
Noble metal alloys
Base metal alloys
Which noble metal alloys are corrosion resistant?
Gold-based
Palladium-based
What does corrosion resistant mean?
Do not form stable oxides
Which metals oxidize to form a chromium oxide surface layer?
Base metals
Which alloy system is stronger: noble metal or base metal?
Base metal alloys
What are the main elements in base metal alloys?
Nickel and Cobalt
When base metals oxidize to form a chromium oxide surface layer, what is blocked? What does this prevent?
Blocks diffusion of oxygen
Prevents corrosion of underlying metal
What are the 3 main noble metals?
Gold (Au)
Platinum (Pt)
Palladium (Pd)
Which metal alloy?
60% noble metals
At least 40% gold
High noble metal alloy
Original PFM alloy (98% nobel metal)
Gold-Platinum-Palladium
First low-gold alternative alloy (50%)
Gold-Palladium-Silver
What improves the castability in the first low-gold alternative alloy?
Silver
Very popular noble metal alloy, has excellent mechanical properties
Palladium-Silver
Which metal alloy?
25% noble metals
No gold requirement
Noble metal alloy
What are the 3 options/combinations for noble metal alloy?
Palladium-Silver
Palladium-Copper-Ga
Palladium-Ga
Which noble metal alloy has 0-2% gold and 30-35% silver?
Palladium-Silver
Which noble metal alloy has at least 70% palladium?
Palladium-Copper-Ga
Which noble metal alloy is a dark oxide that is more difficult to mask, making it not very popular?
Palladium-Ga
What are the 4 options/combinations for base metal alloy?
Nickel-Cr
Be
Nickel
Cobalt-Cr
Which base metal alloy?
Not as burnishable as noble metals (gold, platinum, palladium)
Nickel-Cr
Which base metal alloy?
High modulus of elasticity, ideal for long-span FDPs
Nickel-Cr
Which base metal alloy?
Lower melting point and improves castability
Be
Which base metal alloy?
Toxic; associated with lung and nasal cancer
Nickel
Which base metal alloy?
9% of females are allergic
Nickel
Which base metal alloy?
0.9% of males are allergic
Nickel
Which base metal alloy?
No potential health problems
Co-Cr
Which base metal alloy?
Highest modulus of elasticity
Co-Cr
Which base metal alloy?
Finishing is very difficult
Co-Cr
Which base metal alloy?
High level of hardness
Co-Cr
Due to new advances of digital tech, many of today’s crowns are made with which alloy?
Co-Cr
What technique are Co-Cr alloys printed with?
Selective Laser Melting technique (SLM)
What are PFM and full metal crowns used for?
Single crowns
FDPs (1 or 2 pontics)
If cement films are < than ______ um, then a successful restoration is possible
120
What are the 4 theories of the porcelain/metal attachment mechanism?
Chemical bonding
Compression bonding
Mechanical retention
Van der waals forces (secondary)
The attraction btwn charged atoms that are in intimate contact, yet do not actually exchange electrons
Van der waals forces (secondary)
How are Van der waals forces (secondary) different from chemical bonding (primary)?
There is sharing/exchange of electrons in chemical bonding
The _________ (worse/better) the wetting of the metal surface w/ the liquid porcelain, the greater the Van der waals forces
better
Are Van der waals forces strong or weak?
Weak
How is mechanical retention achieved in metal casting?
Metal cast has microscopic irregularities;
Opaque porcelain flows into irregularities when fired
What kind of surface can porcelain fuse to?
Polished surfaces
T/F: Porcelain does not require a roughened surface to bond to metal, since it can fuse to polished surfaces
True
Air abrasion enhances mechanical retention surface irregularities (stress concentrations) while increasing the overall SA available for bonding
Aluminum oxide
What is porcelain strongest under?
Compression
What is porcelain weakest under?
Tension
If thermal expansion of the metal substructure is greater than that of the porcelain placed over it, the porcelain will ____________ during cooling
compress
When cooling a restoration, the metal contracts _________ (less/more) than the porcelain
more
The difference in contraction rates creates ___________ forces on metal and ______________ forces on porcelain
tensile; compressive
Without a wraparound effect in a full PFM crown, there is _________ (less/more) likelihood that this compression bonding will develop
less
Most significant mechanism
Chemical bonding
Describe the chemical bonding that happens in a crown
Porcelain bonds to oxides of metal substructure
What are the 2 hypotheses of chemical bonding?
Oxide layer bonds to metal on one side and porcelain on other side (grilled cheese)
Metal oxides are dissolved by opaque porcelain layer (2 pieces of bread on top of each other)
In chemical bonding, both covalent and ionic bonds are thought to form, but only a _______________ layer of oxides is believed to be required for chemical bonding to occur
monomolecular (single)
Describe steps of placing opaque porcelain on metal
- Opaque powder mixed w/ distilled water
- Thin wash layer applied w/ brush
- Coping dried & fired under vacuum
- 2nd opaque layer applied to mask the metal
- Coping gently vibrated to condense porcelain & remove excess water
Opaque layer of porcelain should be as ________ as possible, approximately _____ mm thick
thin; 0.3 mm
What type of crown?
Indicated for surveyed crown (RDP), malocclusion, FDP, endo
PFM
FMC
What type of crown?
Indicated when there’s a loss of dental structure
PFM
What type of crown?
Indicated for esthetics
PFM
All ceramic
What type of crown?
When a more conservative restoration is a reliable option
PFM
FMC
What type of crown?
Contraindicated for active caries and perio
PFM
FMC
What type of crown?
Contraindicated for young patients and pulp exposure
PFM
FMC (not as critical as PFM tho)
What type of crown?
Contraindicated when esthetics are an issue
FMC
What type of crown?
Advantage = strong, helps integrity of tooth (compared to onlays/inlays)
PFM
What type of crown?
Advantage = esthetics (compared to full metal)
PFM
All ceramic
What type of crown?
Advantage = permits correction of axial form for RDP tx
PFM
FMC
What type of crown?
Disadvantage = increased removal of dental structure compared to onlays/inlays
PFM (more than FMC)
FMC
What type of crown?
Subgingival margin on anterior segment to achieve esthetics; risk for perio
PFM
How many mm is the metal coping and porcelain on axial wall for PFM crown?
Metal coping = 0.3 mm
Porcelain = 1-1.2 mm
How many mm is the metal coping and porcelain on incisal edge for PFM crown?
Metal coping = 0.3 mm
Porcelain = 1.2-1.7 mm
What does a metal occlusion on a PFM crown allow for?
More conservative prep (as thin as 1 mm)
Stronger occlusal surface (ex: pt with bruxism)
When is a metal occlusion on a PFM crown indicated?
Limited interocclusal clearance
What is one downfall of a metal occlusion on a PFM crown?
Poor esthetics
Dental specialty pertaining to the diagnosis, tx planning, rehab, and maintenance of the oral function, comfort, appearance, and health of pts with clinical conditions associated w/ missing or deficient teeth and/or maxillofacial tissues using biocompatible substitutes
Prosthodontics
Branch of prosthodontics concerned with replacement and/or restoration of teeth by artificial substitutes that are not readily removed from the mouth
Fixed prosthodontics
A fixed prosthodontic restoration that is fabricated outside the pt’s mouth and cemented
Indirect restoration
What are some common indirect restorations?
Inlays
Onlays
Crowns
Bridges
Veneers
What are the 4 main goals of fixed prosthodontics?
Restore function/mastication
Restore aesthetics
Maintain health/integrity of arches
Support tx of problems related to TMJ
Any dental prosthesis that is luted, screwed, or mechanically attached to natural teeth, tooth roots, and dental implant abutments that furnish the primary support for the dental prosthesis
Fixed dental prosthesis (FDP)
Structure that directly receives thrust or pressure; an anchorage. A tooth or dental implant that serves to support and or retain a prosthesis
Abutment
Part of a FDP that unites the abutment to the remainder of the restoration
FDP retainer
Artificial tooth on FDP that replaces a missing tooth, restores its function, and fills the space previously occupied by clinical crown
Pontic
Portion of FDP that unites the retainers and pontics
Connector
Skeletal portion of prosthesis (usually metal) around which and to which are attached the remaining portions of the prosthesis to produce a finished restoration; frequently used to anchor a prosthesis to natural teeth
Framework
Most gingival point of curvature along free gingival margin of a tooth
Gingival trigone/zenith
Why do you want to match the new restoration to the contralateral tooth’s gingival trigone/zenith?
Achieve better esthetics
Where is the gingival trigone/zenith? What is the exception
Distal to center of tooth
exception = lateral incisor, which is in midline
Thin or thick gingiva biotype?
Narrower band of keratinized tissue, which may end in a wavy mucogingival junction
Thin
Thin or thick gingiva biotype?
Perio probe is seen through gingiva while probing
Thin
Thin or thick gingiva biotype?
Wide band of keratinized tissue
Thick
Thin or thick gingiva biotype?
Short papilla
Thick
Thin or thick gingiva biotype?
Squarish teeth
Thick
Thin or thick gingiva biotype?
From occlusal view, the alveolar housing of the teeth is broad
Thick
Thin or thick gingiva biotype?
Presents a thinner buccal plate and gingiva
Thin
Thin or thick gingiva biotype?
Presents a thicker buccal plate and gingiva
Thick
Combined width of CT and JE attachment formed adjacent to a tooth and superior to crestal bone
Biologic width
When prepping a tooth for any kind of restoration, it’s important to place the finish line/margin on what?
Sound dental structure
What happens if the finish line/margin is not placed on sound dental structure?
Higher risk of failure due to multiple margins
What should you do in this situation?
A multi-rooted tooth has had bone loss or has super-erupted, and needs to be evaluated for its perio prognosis (especially on its furcation)
Crown fluting
What does crown fluting allow for?
Cleansability
Slot is incorporated on crown’s surface, coronal to the furcation
Crown fluting
What margin is recommended to conserve as much dental structure as possible when crown fluting?
Feather edge or light chamfer
Why should you round all internal line angles of your prep?
Reduce stress on prep
Less chance of crown breaking/wearing down
Allow crown to seat completely
Used to measure thickness of a crown on a particular area
Crown gauge/caliper
Useful when adjusting a crown/framework where limited space is available
Crown gauge/caliper
What is the absolute minimum thickness of PFM metal coping, occlusal surface of full metal crown, and PFM coping + porcelain?
PFM metal coping: 0.3mm or greater (0.5mm ideally)
Occlusal surface of FMC: 1mm or greater
PFM coping + porcelain: 1.5mm or greater
Describe the steps of removing an existing crown
- Section in equal halves in center of buccal surface - start at margin and finish at lingual surface
- Be sure to cut through all material until cement is exposed
- Break interproximal contact w/ flame diamond
- Use a crown spreader to wedge crown out
No more than ______mm of a layer of porcelain should be applied on a FDP.
If porcelain exceeds this thickness, tell lab to create interproximal contacts in ________ to assure good porcelain support.
2mm; metal
T/F: It is not possible to evaluate your PFM crown and unsupported porcelain on an X-Ray
FALSE; you should be evaluating your crowns/check unsupported porcelain by taking an X-Ray!
How could you theoretically change the PFM crown in order to better support the porcelain and prevent fracture?
Extend design of metal framework
___________ on the porcelain will increase the risk of fracturing a PFM crown
Porosity
Band or ring used to encompass the root or crown of a tooth
Ferrule
Provides a bracing or casing effect to protect integrity of the root
Ferrule
Ferrule height is measured from the build-up core to the crown ________
margin
Ideally, a ferrule effect of how many mm is wanted to minimize the risk of fracture?
1.5-2mm
T/F: A post is NOT contraindicated if the ferrule height of 1.5-2mm is not met, but it compromises its prognosis
True
What are you looking to create to obtain occlusal stability while mounting casts for crown fabrication?
Tripod effect
How do you get the tripod effect for occlusal stability while mounting casts for crown fabrication?
Interocclusal registration
Where should you put the interocclusal registration material?
Only on the teeth you’re restoring
Form of mutually protected articulation in which the vertical and horizontal overlap of canine teeth disengage the posterior teeth in excursive movements of the mandible
Canine protected articulation
The fabrication of a relationship of anterior teeth preventing posterior tooth contact in all eccentric mandibular movements
Anterior guidance
Multiple contact relations between maxillary and mandibular teeth in lateral movements on the working-side whereby simultaneous contact of several teeth act as a group to distribute occlusal forces
Group function
Complete intercuspation of opposing teeth independent of condylar position, sometimes referred to as the best fit of teeth regardless of condylar position
MIP
Occlusion of opposing teeth when mandible is in centric relation; may or may not coincide with MIP
Centric occlusion
Condyles articulate with thinnest avascular portion of respective disks with the complex in the anterio-superior position against the shapes of the articular eminences; independent of tooth contact
Centric relation
Clinically discernible when mandible is directed superior and anteriorly; it is restricted to a purely rotary movement about the transverse horizontal axis
Centric relation
What is essential in preventing secondary caries and perio when prepping a tooth?
Marginal fit of crown
How should the gingival tissue look prior to prep?
Healthy (no inflammation)
T/F: A complete impression of the margin/finish line is necessary
True duh
What must be thoroughly exposed before taking an impression?
Gingival margin of prep
What are the 2 goals when taking a final impression?
Full separation btwn tooth and gingiva
Control of intrasulcular fluid
When is control of intrasulcular fluid critical when taking a final impression?
When hydrophobic impression material is used
What can happen if there is not control of intrasulcular fluid before taking a final impression?
Incomplete margin on impression
Combines chemical action with pressure packing; successful enlargement of gingival sulcus; control of fluids seeping from walls of gingival sulcus
Chemico-mechanical retraction
A sulcular width of _____mm is required to prevent distortion of sulcular impression
0.2mm
Control bleeding and promote tissue retraction; either for pre-impregnation or soaking of retraction cords
Hemostatic agents
What are the 3 requirements for chemical agents in soft tissue management before taking an impression?
Effective in gingival displacement & hemostasis
Absence of irreversible damage to gingiva
Minimal systemic effects
What is used as the vasoconstrictor in hemostatic agents?
Racemic epi
What is racemic epi a combo of?
Levorotatory form of epi + Dextrorotatory form of epi
What are the 2 limitations of vasoconstrictors in hemostatic agents?
Tissue injury (heals in 6-10 days)
Elevate BP/HR
Metal salts that cause contraction of small blood vessels of gingival tissues, producing local tissue contraction and reduced capillary flow
Astringents
Astringents are irritants in ______ concentrations and caustic in ______ concentrations
low; high
Astringents can be what 2 types of sulfate?
Aluminum sulfate compounds
Ferric sulfate
What are the 3 aluminum sulfate compounds for astringents?
Aluminum K+ sulfate
Aluminum sulfate
Aluminum Cl-
Which aluminum sulfate compound for astringents?
100% concentration - less effective than epi but safer
Aluminum K+ sulfate
Which aluminum sulfate compound for astringents?
Effective and biologically acceptable - not sufficient data
Aluminum sulfate
Which aluminum sulfate compound for astringents?
Least irritating; interferes w/ setting of PVS impression material
Aluminum Cl-
Which sulfate compound for astringents?
Very acidic; interferes w/ setting of PVS impression material; stains gingival tissue and all-ceramic crowns
Ferric sulfate
Available in various sizes/designs; gently placed into sulcus to displace gingiva laterally away from tooth
Retraction cord
What are the 3 desirable characteristics of cord?
Color
Absorbent
Different diameters
Which characteristic of cord?
Maximize contrast with gingiva and tooth
Color
Which characteristic of cord?
Allow uptake of liquid medicaments
Absorbent
Which characteristic of cord?
Accommodate the various morphologies of gingival sulcus
Different diameters
What are the 3 types of configurations for retraction cord?
Twisted
Braided
Knitted
Which cord technique?
Impression when gingival tissue is healthy and prep is supragingival
Single cord
Which cord technique?
Placed in the sulcus and removed immediately before impression
Single cord
Which cord technique?
Retraction about the width of the cord
Single cord
Which cord technique?
Often no satisfactory results – tearing of the impression material
Single cord
Which cord technique?
Leads to poor access and collapsed tissue
Single cord
Which cord technique?
Used in single or multiple preps; useful when tissue health is compromised and impression can’t be delayed
Double cord
Which cord technique?
Preferred technique
Double cord
Which cord technique?
Thin cord packed first and left in place for impression
Double cord
Which cord technique?
The second, and thicker, cord is impregnated with hemostatic agent and left in place for ~4-10 min, and removed before impression is taken
Double cord
Which cord technique?
First cord left in place, reducing the tendency of the gingival cuff to recoil and displace impression material
Double cord
Which cord technique?
Better control of gingival hemorrhage and exudates; prevents tearing of impression material
Double cord
Which cord technique?
First cord acts as sulcus liner to protect epithelium
Double cord
Name the retraction cord diameters from smallest to largest
000 to #3
Which cord diameter should be used?
Lower/first cord in double-cord technique
000, 00, 0
Which cord diameter should be used?
Used for front teeth with sensitive and thin gingiva
000
Which cord diameter should be used?
Used for front teeth when prepping/repairing veneers or other subgingival restorations
00, 0
Which cord diameter should be used?
Protection for front teeth and premolars during tooth prep at gum level or subgingival
1
Which cord diameter should be used?
Upper/2nd cord in double cord technique
2, 3
Which cord diameter should be used?
Premolars and molars
2, 3
Which cord diameter should be used?
Posterior teeth with thick, pronounced gingiva
3
Cord overlap should always be in the _________ area, where gingival tissue is bulkier
interproximal
What type of crown?
Advantage = strongest restoration; keeps tooth integrity and doesn’t suffer from porcelain chipping
FMC
What type of crown?
Advantage = most conservative full coverage restoration
FMC
What type of crown?
Disadvantage = not esthetic
FMC
What type of crown?
Disadvantage = electric pulp vitality test can’t be performed
FMC
What are the 4 all ceramic materials for crowns?
Feldspathic porcelain
Lithium disilicate porcelain (Emax)
PFZ
Monolithic zirconia
Which prep design?
Feldspathic porcelain
All ceramic prep
Which prep design?
Lithium dislicate porcelain (Emax)
All ceramic prep
Which prep design?
PFM
PFM prep
Which prep design?
PFZ
PFM prep
Which prep design?
FMC gold
FMC prep
Which prep design?
Monolithic zirconia
FMC prep
What type of crown?
Contraindicated for limited interocclusal space (clearance)
All ceramic
What type of crown?
Difficulty maintaining a dry working field (when bonded)
All ceramic
What type of crown?
Heavy occlusal load (bruxer, opposing an implant supported crown)
All ceramic
What type of crown?
Advantage = wear resistance (but wears opposing natural structure, so always polish)
All ceramic
What type of crown?
Advantage = biocompatible
All ceramic
What type of crown?
Advantage = controlled anatomy and better fit
All ceramic
What type of crown?
Advantage = color stable
All ceramic
What type of crown?
Disadvantage = cost and time
All ceramic
What type of crown?
Disadvantage = brittleness
All ceramic
What type of crown?
Disadvantage = wears opposing dentition (always polish!)
All ceramic
What type of crown?
Disadvantage = repair limitations
All ceramic
What type of crown?
Disadvantage = difficult intraoral finishing
All ceramic
What are the 6 characteristics of all ceramic crowns?
High melting point
Low thermal/electrical conductivity
High compressive strength
Low tensile strength
High hardness
Brittle
What is the thermal requirement of all ceramic crowns? (ON EXAM)
Thermal expansion coefficient < metal
Fuses at a temp < metal
What are the chemical and optical characteristics of all ceramic crowns?
Unaffected by high temp
What are the 6 different ways all ceramic crowns can be classified?
Composition
Translucency
Processing method
Firing temp
Fracture resistance
Abrasiveness
Which type of all ceramic crown?
Predominantly glass
Feldspathic porcelain
Which type of all ceramic crown?
High content of glass
Feldspathic porcelain
Which type of all ceramic crown?
Highly esthetic
Feldspathic porcelain
Which type of all ceramic crown?
Very translucent
Feldspathic porcelain
Which type of all ceramic crown?
Weak ceramic
Feldspathic porcelain
Which type of all ceramic crown?
Particle-filled glass
Lithium disilicate porcelain (Emax)
Which type of all ceramic crown?
Less translucent than feldspathic porcelain
Lithium disilicate porcelain (Emax)
Which type of all ceramic crown?
Stronger ceramic
Lithium disilicate porcelain (Emax)
Which type of all ceramic crown?
Polycrystalline
Zirconia
Which type of all ceramic crown?
No glass; metal oxide
Zirconia
Which type of all ceramic crown?
Tough and less susceptible to crack propagation
Zirconia
Which type of all ceramic crown?
Strongest all ceramic material
Zirconia
Which type of all ceramic crown?
Coefficient of thermal expansion slightly lower than that of metal
Feldspathic porcelain
Which type of all ceramic crown?
Fuses at temp lower than that of metal
Feldspathic porcelain
Which type of all ceramic crown?
Poor conductors
Feldspathic porcelain
Which type of all ceramic crown?
Good compressive strength
Feldspathic porcelain
Which type of all ceramic crown?
High shrinkage after firing
Feldspathic porcelain
Which type of all ceramic crown?
Technique sensitive
Feldspathic porcelain
Which type of all ceramic crown?
Must be etch/bond cemented
Feldspathic porcelain
Which type of all ceramic crown?
Used for all-ceramic restorations and to overlay PFM restorations
Feldspathic porcelain
What are feldspathic porcelain crowns made up of?
Feldspar
Leucite
Quartz (silica)
Kaolin
Glass modifiers
Opacifiers
Color pigments/frits
Glazes
Which component of Feldspathic porcelain?
Naturally occurring minerals composed of Potash (K2O), soda (Na2O), alumina, and silica
Feldspar
Which component of Feldspathic porcelain?
Lowest fusing component, which melts first and flows during firing, initiating these components into a solid mass
Feldspar
Which component of Feldspathic porcelain?
Ground to fine particles and after fusing, it becomes the matrix of the porcelain
Feldspar
Which component of Feldspathic porcelain?
Gives translucency to porcelain
Feldspar
Which component of Feldspathic porcelain?
Crystalline mineral that is formed when feldspar is melted
Leucite
Which component of Feldspathic porcelain?
The greater of this content, the lower risk of crack propagation
Leucite
Which component of Feldspathic porcelain?
Hot-press ceramics have high amounts of these crystals and are considered reinforced glass ceramics
Leucite
Which component of Feldspathic porcelain?
Strengthens the fired porcelain restoration
Quartz (silica)
Which component of Feldspathic porcelain?
Highly refractory; remains unchanged at temp normally used in firing porcelain, and thus contributes stability to mass during heating by providing framework for other ingredients
Quartz (silica)
Which component of Feldspathic porcelain?
Ground to fine particles; acts as a filler in porcelain restoration
Quartz (silica)
Which component of Feldspathic porcelain?
Used as a binder
Kaolin
Which component of Feldspathic porcelain?
Increases moldability of unfired porcelain
Kaolin
Which component of Feldspathic porcelain?
Imparts opacity to finished porcelain product
Kaolin
Which component of Feldspathic porcelain?
Interrupts integrity of quartz (silica) network
Glass modifiers
Which component of Feldspathic porcelain?
Act as flux
Glass modifiers
Which component of Feldspathic porcelain?
Oxides of K+, Na+, Ca2+, or basic oxides
Glass modifiers
Which component of Feldspathic porcelain?
Zirconium, cerium, tin, and uranium oxides
Opacifiers
Which component of Feldspathic porcelain?
Used in the opaque and dentin (body) porcelains
Opacifiers
Which component of Feldspathic porcelain?
Fe/Ni, Cu, MgO, TiO2, and Co oxide
Color pigments/frits
Which component of Feldspathic porcelain?
To provide appropriate shade and characterize restoration (cracks, fissures, etc)
Color pigments/frits
Which component of Feldspathic porcelain?
Fired at low temp
Color pigments/frits
What color is chrome oxide?
Green
What color is cobalt oxide?
Blue
What color is platinum or iron oxide?
Gray
What color is vanadium oxide?
Yellow/brown
What color is chromium-tin oxide?
Pink
Which component of Feldspathic porcelain?
Very high content of feldspar
Glaze
Which component of Feldspathic porcelain?
Purpose is to melt and flow over surface of restoration, giving it a polished/shiny appearance
Glaze
Which component of Feldspathic porcelain?
Diminishes occlusal wear against opposing natural dentition
Glaze
Which component of Feldspathic porcelain?
Low fusing temp
Glaze
Which type of all ceramic crown?
Commercially known as Emax (Ivolcar)
Lithium disilicate
Which type of all ceramic crown?
~70% lithium disilicate crystals
Lithium disilicate
Which type of all ceramic crown?
Stronger than feldspathic porcelain
Lithium disilicate
Which type of all ceramic crown?
Not as esthetic (translucent) as feldspathic porcelain
Lithium disilicate
Which type of all ceramic crown?
No deformation during sintering; doesn’t shrink
Lithium disilicate
Which type of all ceramic crown?
Monochromatic porcelain
Lithium disilicate
Which type of all ceramic crown?
Can be bond cemented or luted
Lithium disilicate
Which type of all ceramic crown?
Hot pressed or milled manufacturing
Lithium disilicate
Which type of all ceramic crown?
Standard composition:
SiO2 (57-80%)
LiO2
K2O
P2O2
ZrO2
ZnO
Lithium disilicate
Which type of Lithium disilicate crown?
“Blue” stage; easier to mill, softer material
Milled
Which type of Lithium disilicate crown?
40% lithium meta-disilicate crystals
Milled
Which type of Lithium disilicate crown?
Treated at 1550 degrees F
Milled
Which type of Lithium disilicate crown?
Crystal size “blue” stage = 0.5 um
Milled
Which type of Lithium disilicate crown?
Crystal size sintered = 3-6 um
Milled
Found naturally as zircon, mainly in Australia, Brazil, India, Russia, South Africa, USA
Zirconium
Zirconium oxide (ZrO2)
Zirconia
At room temp, can be found at it’s monoclinic phase
Zirconia
When heated to 2138 degrees F, it transforms from monoclinic to tetragonal phase, along with a shrinkage of 3-5%
Zirconia
Zirconia + yttrium oxide
Yttria-stabilized zirconia
Maintains tetragonal properties when cooled to room temp; ideal characteristics for dental use
Yttria-stabilized zirconia
Fracture resistant over 1000 MPa
Yttria-stabilized zirconia
Phenomenon whereby a material undergoes one or more phase transformations which result in an almost instantaneous change in volume of that material
Transformation toughening
Triggered by a change in the stress state of
the material, such as an increase in tensile stress, and acts in opposition to the applied stress
Transformation toughening
When zirconia goes from the tetragonal phase to the monoclinic phase, what happens?
Volume increases by 25%
Which type of crown undergoes transformation toughening?
Zirconia
Which type of crown requires a 1mm margin width?
Zirconia
Blocks/pucks are made my highly compressed ___________ powder
zirconia
99.9% of zirconia restorations are made through which system?
CAD/CAM
Zirconia blocks/pucks come partially ________ for milling. Restorations are milled ___________ (25%). They are then fired to 2732 degrees F to fully _______ - this is called the ___________ phase.
fired; oversized; sinter; tetragonal
T/F: Zirconia is only offered as a bright white opaque color
FALSE; at first it could only be offered as a bright white, but now it’s available in different shades/translucencies
The more opaque/less esthetic the crown, the __________ (stronger/weaker) the crown
stronger
The more translucent/esthetic the crown, the ___________ (stronger/weaker) the crown
weaker
What is the most translucent and therefore weakest crown type?
Feldspathic porcelain (predominantly glass)
What crown type is medium translucency and therefore medium strength?
Lithium disilicate (particle-filled glass)
What is the most opaque and therefore the strongest crown type?
Zirconia (polycrystalline)
What are the 4 processing methods to make a crown?
Powder liquid building
Slip casting
Hot-pressed ceramic
Milled (CAD/CAM)
Describe the powder liquid building processing method
- Mix porcelain powder and distilled water
- Ceramic slurry condensed by vibration to remove excess liquid; tissue used to absorb liquid as well
- Avoid voids as it weakens the porcelain
- Placed on furnace to remove moisture and condense porcelain
- Feldspathic porcelain overlaying
Describe the slip-casting processing method
- Porous core infiltrated w/ a lanthanum-based glass
- Produces glassy phase and a crystalline infrastructure (alumina, spinel, zirconia-alumina)
Which processing method is not popular anymore?
Slip-casting
When compared to power liquid building, the slip-casting and hot-pressed ceramics processing methods result in __________ (greater/less) defects and __________ (greater/less) strength
less; greater
Describe the hot-pressed ceramics processing method
- Restoration is waxed using lost-wax technique
- Plasticized ceramic ingot pressed into investment mold
The hot-pressed ceramics processing method is used to make what?
Lithium disilicate crowns
Feldspathic porcelain crowns
Cores
Compared to milling (CAD/CAM), the hot-pressed ceramics processing method results in _________ (better/worse) adaptation of restorations and _________ (greater/less) strength
better; greater
Describe the milled CAD/CAM processing method
Scan prep, design crown, mill
What does CAD/CAM stand for?
Computer aided design
Computer aided manufacturing
The milled CAD/CAM processing method is used to make what?
Single/multiple units
Abutments
Bars
Casts
Guards
Custom trays
Core
What are the popular systems used in the milled CAD/CAM processing method?
E4D
Cerec
iTero
3shape
When compared to powder liquid building, the milled CAD/CAM processing method results in a _________ monolithic block with no _________
solid; bubbles
When compared to hot-pressed ceramics, the milled CAD/CAM processing method results are very __________, but not as good as pressed
accurate
Which processing method is SUPER popular due to time of manufacturing and cost?
Milled CAD/CAM
What is the firing temp of denture teeth?
High-fusing: 2350-2500 degrees F
What is the firing temp of crowns, FDPs, inlays, and onlays?
Medium-fusing: 2000-2350 degrees F
What is the firing temp of veneering on PFM restorations?
Low-fusing: 1600-2000 degrees F
What is the firing temp of titanium and its alloys?
Ultra-low-fusing: <1600 degrees F
What is the fracture resistance of feldspathic porcelain?
100-150 MPa
What is the fracture resistance of pressed lithium disilicate?
400 MPa
What is the fracture resistance of milled lithium disilicate?
360 MPa
What is the fracture resistance of in-ceram alumina using the slip-casting processing method?
600 MPa
What is the fracture resistance of in-ceram spinell using the slip-casting processing method?
250 MPa
What is the fracture resistance of in-ceram zirconia using the slip-casting processing method?
700 MPa
What is the fracture resistance of zirconia and metal framework?
> 1000 MPa
Porcelains are known to _______ the opposing natural dentition
wear
________ (low-fusing porcelains) were developed to finer-sized leucite particles in lower concentrations to reduce abrasiveness
Glazes
Ideally, we want to polish and then ______ porcelains
glaze
Remember to _______ crowns after adjusting occlusion intraorally
polish
___________ is the most abrasive material if not polished, since it is the strongest of all. If left unpolished, it will wear the opposing dentition faster
Zirconia
